Paired Electrosynthesis Of HMF Over Vanadium Nitride-based Electrocatalysts

With the depletion of fossil resources,it is urgent for human to find new alternative resources.Biomass resources have become the current research hotspots because of their renewable and abundant resources.Lignocellulose is an important component of biomass resources,and its downstream products have high added value,such as 5-hydroxymethylfurfural?HMF?can be obtained after hydrolysis,isomerization,and dehydration.HMF is one of the ten most important platform chemicals listed by the US Department of Energy.After oxidation and hydrogenation of HMF,2,5-furandicarboxylic acid?FDCA?,2,5-dimethyltetrahydrofuran?DHMTHF?and other compounds,which are widely used in medicine,fine chemicals,and biodegradable plastics.In recent years,more and more researchers have paid attention to electrocatalytic synthesis technology.Compared with traditional thermocatalysis,it has the advantages of mild reaction conditions,simple operation,and environmental protection.Therefore,the use of electrocatalytic synthesis technology for the conversion of biomass-based compounds has important research significance.In this paper,a vanadium nitride-based catalyst was synthesized,and the electrocatalytic synthesis technology was used to catalyze the oxidation of HMF to FDCA at the anode of the electrode reactor and the catalytic hydrogenation of HMF to DHMTHF at the cathode.?1?A three-dimensional porous hollow nanosphere VN catalyst was prepared by a simple hydrothermal method and high-temperature nitridation.The nanosphere structure of the catalyst is formed by the accumulation of nanoparticles.This morphology will expose a large number of active sites,which is conducive to the adsorption and desorption of the substrate,there by improving the active site utilization rate of the catalyst,and then increasing the ECO performance of HMF.At 60°C,the VN/Ni F electrode was electrolyzed in alkaline electrolyte for 55 minutes.The HMF conversion reached 99%,the FDCA yield reached 97%,and the Faraday efficiency?FE?was 86%.After 8 cycles of reaction,it still has high conversion??98%?,selectivity??96%?,and FE??84%?.Theoretical calculations revealed that the higher performance of VN for the production of ECO could be attributed to its strong chemisorption compared to V₂O₅,which favours HMF activation.Moreover,the transition state energy of HMF oxidation reaction path is calculated,indicating that there are two reaction paths for HMF oxidation,which is consistent with the experimental results.?2?Pd nanoparticles were loaded on the surface of VN by pyrolysis to form a three-dimensional porous hollow nanosphere Pd/VN catalyst.The morphology of the catalyst nanosphere remains unchanged after loading Pd.XPS analysis shows that Pd obtains electrons from V.The strong interaction between Pd and V is conducive to the adsorption and desorption of the reaction substrate HMF,which can improve the activity of HMF electrocatalytic hydrogenation.At 25°C,the Pd/VN/CF electrode was electrolytically reacted in an acidic electrolyte for 45 minutes.HMF conversion reached92%,the DHMTHF yield reached 85%,and the Faraday efficiency was 91%.After 8cycles of reaction,it still maintains good stability?conversion?90%,selectivity?88%,FE?86%?.Both the DFT calculation and the CO dissolution voltammetry experiment show that there is a strong interaction between Pd and VN,and it follows the ECH reaction mechanism.?3?The VN and Pd/VN catalysts were sprayed on bipolar membranes to make CCM?Catalyst Coated Membrane?and assembled into a membrane electrode reactor.The membrane electrode reactor exhibited good electrocatalytic activity in the HMF paired electrosynthesis reaction.At 30°C,the electrolysis was performed at constant current for 180 minutes in an acidic?cathode?and alkaline electrolyte?anode?containing 10 m M HMF.The conversion of anode HMF was 92%,the yield of FDCA was 89%,the conversion of cathode HMF was 87%,and the yield of DHMTHF was77%.This work provides a good reference for the continuous flow of small molecular compound pair electrosynthesis.